Optical data storage medium containing a diaza hemicyanine dye as the light-absorbing compound in the information layer

ABSTRACT

An optical data storage medium containing a preferably transparent substrate which has optionally already been coated with one or more reflecting layers and onto the surface of which a photorecordable information layer, optionally one or more reflecting layers, and optionally a protective layer or an additional substrate or a top layer are applied, which data storage medium can be recorded on and read using blue or red light, preferably laser light, wherein the information layer contains a light-absorbing compound and optionally a binder, characterized in that at least one diaza hemicyanine dye is used as the light-absorbing compound.

[0001] The invention relates to a preferably once recordable optical data storage medium containing a diaza hemicyanine dye as the light-absorbing compound in the information layer, and to a process for its production.

[0002] Recordable optical data storage media using special light-absorbing substances or mixtures thereof are particularly suitable for use in high-density recordable optical data storage media which operate with blue laser diodes, and in particular GaN or SHG laser diodes (360-460 nm), and/or for use in DVD-R or CD-R discs, which operate with red (635-660 nm) or infrared (780-830 nm) laser diodes, and the application of the above-mentioned dyes to a polymer substrate, in particular polycarbonate, by spin-coating or vapour deposition.

[0003] There has recently been an enormous growth in the sales of recordable compact discs (CD-R, 780 nm), which represent the technically established system.

[0004] The next generation of optical data storage media—DVDs—is currently being introduced onto the market. By using shorter-wave laser radiation (635 to660 nm) and a higher numerical aperture NA, the storage density can be increased. The recordable format is in this case the DVD-R.

[0005] Today, optical data storage formats which use blue laser diodes (based on GaN, JP 08191171 or Second Harmonic Generation SHG JP 09050629) (360 nm to 460 nm) with a high laser power, are being developed. Recordable optical data storage media will therefore also be used in this generation. The achievable storage density depends on the focussing of the laser spot in the information plane. The spot size is proportional to the laser wavelength λ/NA. NA is the numerical aperture of the objective lens used. The aim is to use the smallest possible wavelength λ for obtaining the highest possible storage density. Based on semiconductor laser diodes, 390 nm are presently possible.

[0006] The patent literature describes dye-based recordable optical data storage media which are equally suitable both for CD-R and DVD-R systems (JP-A 11 043 481 and JP-A 10 181 206). In order to obtain high reflectivity, a high modulation level of the readout signal and sufficient sensitivity during recording, use is made of the fact that the IR wavelength 780 nm of the CD-R is located at the base of the long-wavelength slope of the absorption peak of the dye and the red wavelength 635 nm or 650 mn of the DVD-R is located at the base of the short-wavelength slope of the absorption peak of the dye. In JP-A 02 557 335, JP-A 10 058 828, JP-A 06 336 086, JP-A 02 865 955, WO-A 09 917 284 and U.S. Pat. No. 5,266,699 this concept is extended to cover the working wavelength range of 450 mn on the short-wavelength slope and the red and IR range on the long-wavelength slope of the absorption peak.

[0007] In addition to the above-mentioned optical properties, the recordable information layer consisting of light-absorbing organic substances must have a morphology which is as amorphous as possible, in order to keep the noise signal during recording or reading as small as possible. For this purpose it is particularly preferable, when applying the substances by spin-coating from a solution or by vapour deposition and/or sublimation, to prevent crystallization of the light-absorbing substances during the subsequent top-coating with metallic or dielectric layers in vacuo.

[0008] The amorphous layer of light-absorbing substances should preferably have high thermal stability, since otherwise additional layers of organic or inorganic material applied by sputtering or vapour deposition onto the light-absorbing information layer form blurred boundaries due to diffusion and thus have an adverse effect on the reflectivity. In addition, if a light-absorbing substance has inadequate thermal stability at the boundary to a polymeric substrate, it can diffuse into the latter and again have an adverse effect on the reflectivity.

[0009] If the light-absorbing substance has too high a vapour pressure, it can sublime during the above-mentioned sputtering or vapour deposition of additional layers in a high vacuum and thus reduce the desired layer thickness. This in turn has a negative effect on reflectivity.

[0010] The object of the invention is therefore to provide suitable compounds which meet the high demands (such as light stability, a favourable signal-to-noise ratio, damage-free application to the substrate material, etc.) for use in the information layer of a recordable optical data storage medium, in particular for high-density recordable optical data storage formats in a laser wavelength range of 340 to 680 nm.

[0011] Surprisingly, it has been found that light-absorbing compounds from the diaza hemicyanine group of dyes are particularly suitable for satisfying the above-mentioned requirement profile.

[0012] The invention therefore relates to an optical data storage medium containing a preferably transparent substrate which has optionally already been coated with one or more reflecting layers and onto the surface of which a photorecordable information layer, optionally one or more reflecting layers and optionally a protective layer or an additional substrate or a top layer are applied, which data storage medium can be recorded on and read using blue or red light, preferably laser light, wherein the information layer contains a light-absorbing compound and optionally a binder, characterized in that at least one diaza hemicyanine dye is used as the light-absorbing compound.

[0013] Blue laser light is particularly preferred.

[0014] The light-absorbing compound should preferably be thermally modifiable. Preferably the thermal modification is carried out at a temperature of <600° C., particularly preferably at a temperature of <400° C., very particularly preferably at a temperature of <300° C., and in particular at a temperature of <200° C. Such a modification can for example be the decomposition or chemical modification of the chromophoric centre of the light-absorbing compound.

[0015] A diaza hemicyanine of the formula (I) is preferred

[0016] in which

[0017] K represents a radical of the formulae (II) to (IV)

[0018] X¹ represents O or S,

[0019] X² represents O, S, CH or N—R²,

[0020] X³ represents N, CH or C—CN,

[0021] R¹, R² and R¹² independently of one another represent C₁- to C₁₆-alkyl, C₃- to C₆-alkenyl, C₅- to C₇-cycloalkyl or C₇- to C₁₆-aralkyl,

[0022] A together with X² and the C-atom bound therebetween represents a five-membered aromatic or quasi-aromatic heterocyclic ring which can contain 1 to 4 hetero atoms and/or can be benzo- or naphtho-fused and/or substituted by non-ionic radicals,

[0023] R³, R⁴, R⁵ and R⁶ independently of one another represent hydrogen, C₁- to C₁₆-alkyl, C₄- to C₇-cycloalkyl, C₇- to C₁₆-aralkyl or a heterocyclic radical or

[0024] NR³R⁴ or NR⁵R⁶ independently of one another represent a five- or six-membered saturated ring which is attached via N and can additionally contain an N or O atom and/or be substituted by non-ionic radicals,

[0025] R⁷ represents hydrogen, C₁- to C₁₆-alkyl, C₁- to C₁₆-alkoxy or halogen or

[0026] R⁷ and R⁵ form a two- or three-membered bridge which can contain an O or N atom and/or be substituted by non-ionic radicals,

[0027] R⁸ represents hydrogen, C₁- to C₁₆-alkyl, C₁- to C₁₆-alkoxy, halogen, cyano, C₁-to C₄-alkoxycarbonyl, O—CO—R¹⁰, NH—CO-R¹⁰, O-SO₂-R¹⁰ or NH—SO₂-R¹⁰,

[0028] R⁹ represents hydrogen, C₁- to C₄-alkyl or C₆- to C₁₀-aryl,

[0029] R¹⁰ represents hydrogen, C₁- to C₁₆-alkyl, C₄- to C₇-cycloalkyl, C₇- to C₁₆-aralkyl, C₁- to C₁₆-alkoxy, mono- or bis-C₁- to C₁₆-alkylamino, C₆- to C₁₀-aryl, C₆- to C₁₀-aryloxy, C₆- to C₁₀-arylamino or a heterocyclic radical,

[0030] R¹¹ represents hydrogen, C₁- to C₄-alkyl or C₆- to C₁₀-aryl and

[0031] An⁻ represents an anion.

[0032] Suitable non-ionic radicals are for example C₁- to C₄-alkyl, C₁- to C₄-alkoxy, halogen, cyano, nitro, C₁- to C₄-alkoxycarbonyl, C₁- to C₄-alkylthio, C₁- to C₄-alkanoylanino, benzoylamino, mono- or di-C₁- to C₄-alkylamino.

[0033] Alkyl, alkoxy, aryl and heterocyclic radicals can optionally contain additional radicals such as alkyl, halogen, nitro, cyano, CO—NH₂, alkoxy, trialkylsilyl, trialkyl-siloxy or phenyl, the alkyl and alkoxy radicals can be straight-chain or branched, the alkyl radicals can be partially halogenated or perhalogenated, the alkyl and alkoxy radicals can be ethoxylated or propoxylated or silylated, adjacent alkyl and/or alkoxy radicals on aryl or heterocyclic radicals can together form a three- or four-membered bridge and the heterocyclic radicals can be benzo-fused and/or quatemized.

[0034] The ring A of the formula

[0035] particularly preferably represents thiazol-2-yl, benzothiazol-2-yl, benzoxazol-2-yl, benzimidazol-2-yl, imidazol-2-yl, pyrazol-3-yl, 1,3,4-triazol-2-yl, 1,3,4-thiadiazol-2-yl, 1,2,4-thiadiazol-5-yl, 2- or 4-pyridyl or 2- or 4-quinolyl, wherein the aforementioned rings can each be substituted by C₁- to C₆-alkyl, C₁- to C₆-alkoxy, fluorine, chlorine, bromine, iodine, cyano, nitro, C₁- to C₆-alkoxycarbonyl, C₁- to C₆-alkylthio, C₁- to C₆-acylamino, C₆- to C₁₀-aryl, C₆- to CI₀-aryloxy, C₆- to C₁₀-arylcarbonylamino, mono- or di-C₁- to C₆-alkylamino, N—C₁- to C₆-alkyl-N—C₆- to C₁₀-arylamino, pyrrolidino, morpholino or piperazino.

[0036] In a particularly preferred form the diaza hemicyanines used are those of the formula (I),

[0037] in which

[0038] the ring A of the formula

[0039] represents thiazol-2-yl, benzothiazol-2-yl, wherein X² represents S and the aforementioned radicals can each be substituted by methyl, ethyl, methoxy, ethoxy, chlorine, cyano, methoxycarbonyl or ethoxycarbonyl, or represents 1,3,4-triazolyl or 1,3,4-thiadiazolyl, wherein X² represents N—R² or S, respectively, and the aforementioned radicals can each be substituted by methyl, ethyl, phenyl, methoxy, ethoxy, methylthio, ethylthio, amino, anilino, dimethylamino, diethylamino, dipropylamino, dibutylamino, N-methyl-N-cyanethylamino, N-methyl-N-hydroxy-ethylamino, N-methyl-N-phenylamino, di-(cyanethyl)amino, di-(hydroxyethyl)amino, cyanethylamino, hydroxyethylamino, pyrrolidino, piperidino, morpholino or a radical of the formula

[0040] K represents a radical of the formulae (II), (III) or (IV),

[0041] X¹ represents O or S,

[0042] X³ represents N, CH or C—CN,

[0043] R¹, R² and R¹² independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, phenethyl, phenylpropyl, allyl, cyclohexyl, chloroethyl, cyanomethyl, cyanoethyl, cyanopropyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl or ethoxyethyl,

[0044] R³, R⁴, R⁵ and R⁶ independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, phenethyl, phenylpropyl, cyclohexyl, chloroethyl, cyanomethyl, cyanoethyl, cyanopropyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxycarbonylethyl, acetoxyethyl, propionyloxyethyl or a radical of the formula

[0045] and R³ and R⁵ can additionally represent hydrogen or

[0046] NR³R⁴ and NR⁵R⁶ independently of one another represent pyrrolidino, piperidino, N-methylpiperazino, N-ethylpiperazino, N-hydroxyethylpiperazino or morpholino,

[0047] R⁷ represents hydrogen, methyl, methoxy or chlorine or

[0048] R⁷; R⁵ represent a —(CH₂)₂—, —(CH₂)₃—, —C(CH₃)—CH₂—C(CH₃)₂— or —O—(CH₂)₂— bridge,

[0049] R⁸ represents hydrogen, methyl, methoxy or chlorine,

[0050] R⁹ represents hydrogen,

[0051] R¹¹ represents hydrogen, methyl or phenyl and

[0052] An⁻ represents an anion.

[0053] Suitable anions An⁻ are all monovalent anions or one equivalent of a polyvalent anion. Preferably the anions are colourless. Suitable anions are, for example, chloride, bromide, iodide, tetrafluoroborate, perchlorate, hexafluorosilicate, hexafluorophosphate, methosulphate, ethosulphat, C₁- to C₁₀-alkanesulphonate, C₁- to C₁₀-perfluoroalkane sulphonate, C₁- to C₁₀-alkanoate optionally substituted by chlorine, hydroxyl or C₁- to C₄ alkoxy, benzene sulphonate, naphthalene sulphonate or biphenyl sulphonate optionally substituted by nitro, cyano, hydroxyl, C₁- to C₂₅-alkyl, perfluoro-C₁- to C₄-alkyl, C₁- to C₄-alkoxycarbonyl or chlorine, benzene disulphonate, naphthalene disulphonate or biphenyl disulphonate optionally substituted by nitro, cyano, hydroxyl, C₁- to C₄-alkyl, C₁- to C₄-alkoxy, C₁- to C₄-alkoxycarbonyl or chlorine, benzoate optionally substituted by nitro, cyano, C₁- to C₄-alkyl, C₁- to C₄-alkoxy, C₁- to C₄-alkoxycarbonyl, benzoyl, chlorobenzoyl or toluoyl, the anion of naphthalenedicarboxylic acid, diphenyl ether disulphonate, tetraphenyl borate, cyanotriphenyl borate, tetra-C₁- to C₂₀-alkoxyborate, tetraphenoxyborate, 7,8- or 7,9-dicarba-nido-undecaborate(1-) or (2-), which are optionally substituted on the B- and/or C-atoms by one or two C₁- to C₁₂-alkyl or phenyl groups, dodecahydro-dicarbadodecaborate(2-) or B—C₁- to C₁₂-alkyl-C-phenyl-dodecahydro-dicarbadodecaborate(1-).

[0054] Bromide, iodide, tetrafluoroborate, perchlorate, methane sulphonate, benzene sulphonate, toluene sulphonate, dodecylbenzene sulphonate and tetradecane sulphonate are preferred.

[0055] In a very particularly preferred form the diaza hemicyanines used are those of the formulae (VI) to (IX)

[0056] in which

[0057] R¹ and R² independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanomethyl, cyanoethyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl or a radical of the formula

[0058] R⁵ and R⁶ independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanoethyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxycarbonylethyl or acetoxyethyl or

[0059] NR⁵R⁶ represents pyrrolidino, piperidino or morpholino,

[0060] R⁷ represents hydrogen or

[0061] R⁷; R⁵ represent a —(CH₂)₂—, —C(CH₃)—CH₂—C(CH₃)₂— or —O—(CH₂)₂— bridge,

[0062] R⁸ represents hydrogen,

[0063] R¹³, R¹⁴ and R¹⁵ independently of one another represent hydrogen, methyl, methoxy, chloro, nitro or cyano,

[0064] R¹⁶ and R¹⁷ independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanoethyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxycarbonylethyl, acetoxyethyl or phenyl and

[0065] R¹⁶ additionally represents hydrogen or

[0066] NR¹⁶R¹⁷ represents pyrrolidino, piperidino or morpholino, and

[0067] An^(− represents tetrafluoroborate, perchlorate, hexafluorosilicate, hexafluorophosphate, iodide, rhodanide, cyanate, hydroxy acetate, methoxy acetate, lactate, citrate, methane sulphonate, ethane sulphonate, benzene sulphonate, toluene sulphonate, butylbenzene sulphonate, chlorobenzene sulphonate, dodecylbenzene sulphonate or naphthalene sulphonate,)

[0068] wherein all alkyl radicals can be branched.

[0069] In a very particularly preferred form the diaza hemicyanines used are those of the formulae (X) to (XIII)

[0070] in which

[0071] R¹ and R² independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanomethyl, cyanoethyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl or a radical of the formula

[0072] X¹ represents O and

[0073] X³ represents CH or

[0074] X¹ represents S and

[0075] X³ represents N, CH or C—CN,

[0076] R³ and R⁴ independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chioroethyl, cyanoethyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxycarbonylethyl or acetoxyethyl or

[0077] NR³R⁴ represents pyrrolidino, piperidino or morpholino,

[0078] R⁹ represents hydrogen,

[0079] R¹³, R¹⁴ and R¹⁵ independently of one another represent hydrogen, methyl, methoxy, chloro, nitro or cyano,

[0080] R¹⁶ and R¹⁷ independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanoethyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxycarbonylethyl, acetoxyethyl or phenyl and

[0081] R¹⁶ additionally represents hydrogen or

[0082] NR¹⁶R¹⁷ represents pyrrolidino, piperidino or morpholino, and

[0083] An⁻ represents tetrafluoroborate, perchlorate, hexafluorosilicate, hexafluorophosphate, iodide, rhodanide, cyanate, hydroxy acetate, methoxy acetate, lactate, citrate, methane sulphonate, ethane sulphonate, benzene sulphonate, toluene sulphonate, butylbenzene sulphonate, chlorobenzene sulphonate, dodecylbenzene sulphonate or naphthalene sulphonate,

[0084] wherein all alkyl radicals can be branched.

[0085] In a very particularly preferred form the diaza hemicyanines used are those of the formulae (XIV) to (XVII)

[0086] in which

[0087] R¹, R² and R¹² independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanomethyl, cyanoethyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl or a radical of the formula

[0088] R¹³, R¹⁴ and R¹⁵ independently of one another represent hydrogen, methyl, methoxy, chloro, nitro or cyano,

[0089] R¹⁶ and R¹⁷ independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanoethyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxycarbonylethyl, acetoxyethyl or phenyl and

[0090] R¹⁶ additionally represents hydrogen or

[0091] NR¹⁶R¹⁷ represents pyrrolidino, piperidino or morpholino,

[0092] R¹¹ represents hydrogen, methyl or phenyl and

[0093] An⁻ represents tetrafluoroborate, perchlorate, hexafluorosilicate, hexafluorophosphate, iodide, rhodanide, cyanate, hydroxy acetate, methoxy acetate, lactate, citrate, methane sulphonate, ethane sulphonate, benzene sulphonate, toluene sulphonate, butylbenzene sulphonate, chlorobenzene sulphonate, dodecylbenzene sulphonate or naphthalene sulphonate,

[0094] wherein all alkyl radicals can be branched.

[0095] In a very particularly preferred form the diaza hemicyanines used are those of the formulae (IX), (XIII) and (XVII).

[0096] For a recordable optical data storage medium according to the invention which is recorded on and read using light from a blue laser, such diaza hemicyanine dyes are preferred whose absorption maximum λ_(max2) is in the range from 420 to 550 nm, wherein the wavelength λ_(½) at which the extinction on the short-wavelength slope of the absorption maximum of the wavelength λ_(max2) is half the extinction value at λ_(max2,) and the wavelength λ_({fraction (1/10)}), at which the extinction on the short-wavelength slope of the absorption maximum of the wavelength λ_(max2) is a tenth of the extinction value at λ_(max2), are preferably in each case no further than 50 nm away from each other. Preferably such a diaza hemicyanine dye does not display a shorter-wave maximum λ_(max1) at a wavelength below 350 nm, particularly preferably below 320 nm, and very particularly preferably below 290 nm.

[0097] Preferred diaza hemicyanine dyes are those with an absorption maximum λ_(max2) of 410 to 530 nm.

[0098] Particularly preferred diaza hemicyanine dyes are those with an absorption maximum λ_(max2) of 420 to 510 nm.

[0099] Very particularly preferred diaza hemicyanine dyes are those with an absorption maximum λ_(max2) of 430 to 500 nm.

[0100] In these diaza hemicyanine dyes λ_(½) and λ_({fraction (1/10)}), as defined above, are preferably no further than 40 nm, particularly preferably no further than 30 nm, and very particularly preferably no further than 20 nm away from each other.

[0101] For a recordable optical data storage medium according to the invention which is recorded on and read using light from a red laser, such diaza hemicyanine dyes are preferred whose absorption maximum λ_(max2) is in the range from 500 to 650 nm, wherein the wavelength λ_(½) at which the extinction on the long-wavelength slope of the absorption maximum of the wavelength λ_(max2) is half the extinction value at λ_(max2), and the wavelength λ_({fraction (1/10)}), at which the extinction on the long-wavelength slope of the absorption maximum of the wavelength λ_(max2) is a tenth of the extinction value at λ_(max2), are preferably in each case no further than 50 mn away from each other. Preferably such a diaza hemicyanine dye does not display a longer-wave maximum λ_(max')at a wavelength below 750 nm, particularly preferably below 800 nm, and very particularly preferably below 850 nm.

[0102] Preferred diaza hemicyanine dyes are those with an absorption maximum λ_(max2) Of 530 to 630 nm.

[0103] Particularly preferred diaza hemicyanine dyes are those with an absorption maximum λ_(max2) of 550 to 620 nm.

[0104] Very particularly preferred diaza hemicyanine dyes are those with an absorption maximum λ_(max2) of 580 to 610 nm.

[0105] In these diaza hemicyanine dyes λ_(½) and λ_({fraction (1/10)}), as defined above, are preferably no further than 40 um, particularly preferably no further than 30 um, and very particularly preferably no further than 20 nm away from each other.

[0106] At the absorption maximum λ_(max2) the diaza hemicyanine dyes have a molar extinction coefficient ε of >30000 1/mol cm, preferably >40000 1/mol cm, particularly preferably >50000 1/mol cm and very particularly preferably >70000 1/mol cm.

[0107] The absorption spectra are, for example, measured in solution.

[0108] Suitable diaza hemicyanines having the required spectral properties are in particular those in which the change in the dipole moment Δμ=|μ_(g)−μ_(ag)|, i.e. the positive difference between the dipole moments in the ground state and the first excited state is as small as possible, i.e. preferably <5 D, and particularly preferably <2 D. A method of determining such a change in the dipole moment Δμ is described, for example, in F. Würthner et al., Angew. Chem. 1997, 109, 2933 and in the literature cited therein. Low solvatochromism (methanol/methylene chloride) is also a suitable criterion for selection. Preferred diaza hemicyanines are those whose solvatochromism Δλ=|λ_(methylene chloride)-λ_(methanol)|, i.e. the positive difference between the absorption wavelengths in the solvents methylene chloride and methanol, is <25 nm, particularly preferably <15 nm, and very particularly preferably <5 nm.

[0109] Diaza hemicyanines of the formulae (I) and (VI) to (XVII) are known, for example, from BE 825 455,DE-OS 1 044 023, DE-OS 2 811 258, DE-OS 1 163 775.

[0110] Another part of the invention are diaza hemicyanines of formula (I), wherein K means a radical of formula (III) and the other residues have the above meaning. Another special part of the invention are diaza hemicyanines of the formulae (X), (XI), (XII) or (XIII), wherein the residues have the above meaning.

[0111] The light-absorbing substances described guarantee sufficiently high reflectivity (>10%) of the optical data storage medium in the unrecorded state and sufficiently high absorption for the thermal degradation of the information layer upon spotwise illumination with focussed light, if the wavelength of the light is in the range from 360 to 460 nm and 600 to 680 nm. The contrast between the recorded and unrecorded areas of the data storage medium is effected by the change in reflectivity in terms of the amplitude as well as the phase of the incident light as a result of the changed optical properties of the information layer following thermal degradation.

[0112] The diaza hemicyanine dyes are preferably applied to the optical data storage medium by spin-coating or vacuum coating. The diaza hemicyanines can be mixed with other dioaza hemicyanines or with other dyes having similar spectral properties. The information layer can contain additives in addition to the diaza hemicyanine dyes, such as binders, wetting agents, stabilizers, diluents and sensitizers as well as other constituents.

[0113] In addition to the information layer, the optical data storage medium can contain other layers such as metal layers, dielectric layers and protective layers. Metals and dielectric layers are used, for example, for adjusting the reflectivity and the thermal balance. Depending on the laser wavelength, the metals can be gold, silver or aluminium, etc. Dielectric layers are, for example, silicon dioxide and silicon nitride. Protective layers are, for example, photocurable surface coatings, adhesive layers and protective films.

[0114] Adhesive layers can consist of a pressure-sensitive material.

[0115] Pressure-sensitive adhesive layers consist mainly of acrylic adhesives. Nitto Denko DA-8320 or DA-8310, which are disclosed in the patent JP-A 11-273147, can, for example, be used for this purpose.

[0116] The optical data storage medium has, for example, the following layer assembly (cf. FIG. 1): a transparent substrate (1), optionally a protective layer (2), an information layer (3), optionally a protective layer (4), optionally an adhesive layer (5) and a top layer (6).

[0117] Preferably, the optical data storage medium assembly can contain:

[0118] a preferably transparent substrate (1), onto whose surface at least one photorecordable information layer (3), which can be recorded on using light, preferably laser light, optionally a protective layer (4), optionally an adhesive layer (5) and a transparent top layer (6) are applied;

[0119] a preferably transparent substrate (1), onto whose surface a protective layer (2), at least one information layer (3) which can be recorded on using light, preferably laser light, optionally an adhesive layer (5) and a transparent top layer (6) are applied;

[0120] a preferably transparent substrate (1), onto whose surface optionally a protective layer (2), at least one information layer (3) which can be recorded on using light, preferably laser light, optionally a protective layer (4), optionally an adhesive layer (5) and a transparent top layer (6) are applied;

[0121] a preferably transparent substrate (1), onto whose surface at least one information layer (3) which can be recorded on using light, preferably laser light, optionally an adhesive layer (5) and a transparent top layer (6) are applied.

[0122] Alternatively, the optical data storage medium has for example the following layer assembly (cf. FIG. 2): a preferably transparent substrate (11), an information layer (12), optionally a reflecting layer (13), optionally an adhesive layer (14) and an additional, preferably transparent, substrate (15).

[0123] The invention also relates to optical data storage media according to the invention which are recorded on using blue or red light, in particular laser light.

[0124] The following examples illustrate the subject matter of the invention:

EXAMPLES Example 1

[0125] 4 g of 2-amino-5-(diisopropylamino)-1,3,4-thiadiazole were dissolved in 40 ml of glacial acetic acid. 8 ml of 85% by weight phosphoric acid and 6 ml of 48% by weight sulphuric acid were added dropwise at 10° C. 6.8 g of nitrosylsulphuric acid (40% by weight in sulphuric acid) were then added dropwise at 5° C. over a period of 30 mins.. After 4 h at 0-5° C. the nitrite excess was destroyed with amidosulphonic acid.

[0126] This diazotized product was added dropwise at 10° C. over a period of 1 hour to a solution of 5 g of 2-morpholino-4-phenylthiazole in 30 ml of glacial acetic acid, a pH of 3 being maintained with a 20% by weight aqueous soda solution. After stirring overnight at a pH of 3.5 the mixture was filtered off with suction and the residue was washed with water. The solid was stirred into 100 ml of water and the mixture was adjusted to a pH of 7.5, filtered off with suction once again and the residue was washed with water. After drying, the crude product was dissolved in 100 ml of toluene. By slowly adding 400 ml of hexane with stirring, the product was precipitated, filtered off with suction, washed with hexane and afterwards with water and dried. 3.7 g (41% of theory) of a violet powder of the formula

[0127] was obtained.

[0128] M.p.=155° C.

[0129] λ_(max)(dioxane)=531 nm.

[0130] 2.3 g of the above azo dye were dissolved in 20 ml of glacial acetic acid. 1.3 g of dimethyl sulfate were added and the mixture was stirred at 70° C. for 5 hours. After cooling to room temperature 200 ml of water were added. The solution was extracted with 50 ml of toluene and afterwords with 100 ml of chloroform. The chloroform phase was evaporated to dryness. The resulting violet dye was solved in 30 ml of methanol. 0.6 g of lithium perchlorate were added. After stirring over night the precipitated product was filtered off with suction, washed with methanol and dried. 1.5 g (53% of theory) of a violet powder of the formula

[0131] was obtained.

[0132] λ_(max)(methanol)=592 nm

[0133] ε=30100 1/mol cm

[0134] Solubility: >2% in TFP (2,2,3,3-tetrafluoropropanol)

[0135] a glassy film

[0136] Diaza hemicyanine dyes which are also suitable are listed in the table: Ex.

K An⁻ λ_(max)/nm¹⁾ ε/l/mol cm λ_(1/2)- λ_(1/10)/nm Δλ²⁾/nm  2

CH₃OSO₃ ⁻ 508 36570  3 ″

ClO₄ ⁻ 602 79750 21⁴⁾  4

ClO₄ ⁻ 580 56200  5

″ ClO₄ ⁻ 582 56800  6 ″

ClO₄ ⁻ 610  7 ″

ClO₄ ⁻ 588  8 ″

BF₄ ⁻ 590 47900  9 ″

BF₄ ⁻ 590 52100 10 ″

BF₄ ⁻ 600 56010 24⁴⁾ 11 ″

BF₄ ⁻ 589 56680 12 ″

BF₄ ⁻ 568 13

″ ClO₄ ⁻ 583 60260 14

ClO₄ ⁻ 602 59430 15

″ ClO₄ ⁻ 599 67110 23⁴⁾ 16 ″

ClO₄ ⁻ 587 82300 10 17

″ ClO₄ ⁻ 606 74560 23⁴⁾ 18

ClO₄ ⁻ 606 77260 21⁴⁾ 19 ″

PF₆ ⁻ 592 77300 20 ″

BF₄ ⁻ 587 72570 21

BF₄ ⁻ 601 82610 22

″ PF₆ ⁻ 599 56320 23

BF₄ ⁻ 597 63100 24

BF₄ ⁻ 597 76600 12 25

ClO₄ ⁻ 588 54700 26

BF₄ ⁻ 526 53970 42³⁾18⁴⁾ 27 ″

ClO₄ ⁻ 492 52100 28 ″

Br⁻ 460 29

ClO₄ ⁻ 538 30

″ ClO₄ ⁻ 534 31

ClO₄ ⁻ 465 32

ClO₄ ⁻ 495 33

ClO₄ ⁻ 590 34

″ ClO₄ ⁻ 593 35

BF₄ ⁻ 586 62000 36 ″

BF₄ ⁻ 601 67750 37 ″

CH₃SO₃ ⁻ 607 71480 15 38

BF₄ ⁻ 591

Example 39

[0137] A 4% by weight solution of the dye of Example 27 in 2,2,3,3-tetrafluoropropanol was prepared at room temperature. This solution was applied by means of spin-coating to a pre-grooved polycarbonate substrate. The pre-grooved polycarbonate substrate was produced in the form of a disc by injection-moulding. The dimensions of the disc and the groove structure corresponded to those usually employed for DVD-R's. The disc containing the dye layer as the information carrier was vapour-plated with 100 nm of silver. Then a UV-curable acrylic lacquer was applied by spin-coating and cured using a UV lamp. Using a dynamic recording test setup constructed on an optical bench and consisting of a diode laser (λ=405 nm) for producing linearly polarized light, a polarization-sensitive beam splitter, a λ/4-plate and a movably suspended collective lens with a numerical aperture NA of 0.65 (actuator lens), experiments on the recording (writing) and reading of data were carried out. The light reflected from the reflecting layer of the disc was coupled out of the beam path with the aid of the abovementioned polarization-sensitive beam splitter and focussed onto a four-quadrant detector through an astigmatic lens. At a linear velocity of V=2.6 m/s and a recording (writing) power of P_(W)=13.2 mW a signal-to-noise ratio of C/N=42 dB was measured. The recording power was applied as an oscillating pulse sequence, the disc being irradiated alternately for 1 μs with the abovementioned recording power P_(W) and for 4 μs with the reading power P_(r) ≈0.44 mW. The disc was irradiated with this oscillating pulse sequence until it had turned completely a single time. Then the marking produced was read with a reading power P_(r)≈0.44 mW and the abovementioned signal-to-noise ratio C/N was determined.

[0138] Optical data storage media were obtained analogously using the other examples from the above table. 

1. An optical data storage medium containing a preferably transparent substrate which has optionally already been coated with one or more reflecting layers and onto the surface of which a photorecordable information layer, optionally one or more reflecting layers and optionally a protective layer or an additional substrate or a top layer are applied, which data storage medium can be recorded on and read using blue or red light, preferably laser light, wherein the information layer contains a light-absorbing compound and optionally a binder, characterized in that at least one diaza hemicyanine dye is used as the light-absorbing compound.
 2. An optical data storage medium according to claim 1, characterized in that the hemicyanine corresponds to the formula (I)

in which K represents a radical of the formulae (II) to (IV)

X¹ represents O or S, X² represents O, S, CH or N—R², X³ represents N, CH or C—CN, R¹, R² and R¹² independently of one another represent C₁- to C₁₆-alkyl, C₃- to C₆-alkenyl, C₅- to C₇-cycloalkyl or C₇- to C₁₆-aralkyl, A together with X² and the C-atom bound therebetween represents a five-membered aromatic or quasi-aromatic heterocyclic ring which can contain 1 to 4 hetero atoms and/or can be benzo- or naphtho-fused and/or substituted by non-ionic radicals, R³, R⁴, R⁵ and R⁶ independently of one another represent hydrogen, C₁- to C₁₆-alkyl, C₄- to C₇-cycloalkyl, C₇- to C₁₆-aralkyl or a heterocyclic radical or NR³R⁴ or NR⁵R⁶ independently of one another represent a five- or six-membered saturated ring which is attached via N and can additionally contain an N or O atom and/or be substituted by non-ionic radicals, R⁷ represents hydrogen, C₁- to C₁₆-alkyl, C₁- to C₁₆-alkoxy or halogen or R⁷ and R⁵ form a two- or three-membered bridge which can contain an O or N atom and/or be substituted by non-ionic radicals, R⁸ represents hydrogen, C₁- to C₁₆-alkyl, C₁- to C₁₆-alkoxy, halogen, cyano, C₁- to C₄-alkoxycarbonyl, O—CO—R¹⁰, NH—CO—R¹⁰, O—SO₂-R¹⁰ or NH—SO₂-R¹⁰, R⁹ represents hydrogen, C₁- to C₄-alkyl or C₆- to C₁₀-aryl, R¹⁰ represents hydrogen, C₁- to C₁₆-alkyl, C₄- to C₇-cycloalkyl, C₇- to C₁₆-aralkyl, C₁- to C₁₆-alkoxy, mono- or bis-C₁- to C₁₆-alkylamino, C₆- to C₁o-aryl, C₆- to C₁₀-aryloxy, C₆- to C₁₀-arylamino or a heterocyclic radical, R¹¹ represents hydrogen, C₁- to C₄-alkyl or C₆- to C₁₀-aryl and An⁻ represents an anion.
 3. An optical data storage medium according to claim 2, characterized in that in the formula (I) the ring A of the formula

particularly preferably represents thiazol-2-yl, benzothiazol-2-yl, benzoxazol-2-yl, benzimidazol-2-yl, imidazol-2-yl, pyrazol-3-yl, 1,3,4-triazol-2-yl, 1,3,4-thiadiazol-2-yl, 1,2,4-thiadiazol-5-yl, 2- or 4-pyridyl or 2- or 4-quinolyl, wherein the aforementioned rings can each be substituted by C₁- to C₆-alkyl, C₁- to C₆-alkoxy, fluorine, chlorine, bromine, iodine, cyano, nitro, C₁- to C₆-alkoxycarbonyl, C₁- to C₆-alkylthio, C₁- to C₆-acylamino, C₆- to C₁₀-aryl, C₆-to C₁₀-aryloxy, C₆- to C₁₀-arylcarbonylamino, mono- or di-C₁- to C₆-alkyl-amino, N—C₁- to C₆-alkyl-N—C₆- to C₁₀-arylamino, pyrrolidino, morpholino or piperazino.
 4. An optical data storage medium according to one or more of claims 2 to 3, characterized in that the diaza hemicyanine corresponds to the formula (I), in which the ring A of the formula

represents thiazol-2-yl, benzothiazol-2-yl, wherein X² represents S and the aforementioned radicals can each be substituted by methyl, ethyl, methoxy, ethoxy, chlorine, cyano, methoxycarbonyl or ethoxycarbonyl, or represents 1,3,4-triazolyl or 1,3,4-thiadiazolyl, wherein X² represents N—R² or S, respectively, and the aforementioned radicals can each be substituted by methyl, ethyl, phenyl, methoxy, ethoxy, methylthio, ethylthio, amino, anilino, dimethylamino, diethylamino, dipropylamino, dibutylamino, N-methyl-N-cyanethylamino, N-methyl-N-hydroxyethylamino, N-methyl-N-phenylamino, di-(cyanethyl)amino, di-(hydroxyethyl)amino, cyanethylamino, hydroxyethylamino, pyrrolidino, piperidino, morpholino or a radical of the formula

K represents a radical of the formulae (II), (III) or (IV), X¹ represents O or S, X³ represents N, CH or C—CN, R¹, R² and R¹² independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, phenethyl, phenylpropyl, allyl, cyclohexyl, chloroethyl, cyanomethyl, cyanoethyl, cyanopropyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl or ethoxyethyl, R³, R⁴, R⁵ and R⁶ independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, phenethyl, phenylpropyl, cyclohexyl, chloroethyl, cyanomethyl, cyanoethyl, cyanopropyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxycarbonylethyl, acetoxyethyl, propionyloxyethyl or a radical of the formula

and R³ and R⁵ can additionally represent hydrogen or NR³R⁴ and NR⁵R⁶ independently of one another represent pyrrolidino, piperidino, N-methylpiperazino, N-ethylpiperazino, N-hydroxyethyl-piperazino or morpholino, R⁷ represents hydrogen, methyl, methoxy or chlorine or R⁷; R⁵ represent a —(CH₂)₂—, —(CH₂)₃—, —C(CH₃)—CH₂—C(CH₃)₂— or —O—(CH₂)₂— bridge, R⁸ represents hydrogen, methyl, methoxy or chlorine, R⁹ represents hydrogen, R¹¹ represents hydrogen, methyl or phenyl and An^(—) represents an anion.
 5. An optical data storage medium according to one or more of claims 1 to 4, characterized in that the diaza hemicyanine corresponds to the formula (VI) to (IX)

in which R¹ and R² independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanomethyl, cyanoethyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl or a radical of the formula

R⁵ and R⁶ independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanoethyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxycarbonylethyl or acetoxyethyl or NR⁵R⁶ represents pyrrolidino, piperidino or morpholino, R⁷ represents hydrogen or R⁷; R⁵ represent a —(CH₂)₂—, —C(CH₃)—CH₂—C(CH₃)₂— or —O—(CH₂)₂— bridge, R⁸ represents hydrogen, R¹³, R¹⁴ and R¹⁵ independently of one another represent hydrogen, methyl, methoxy, chloro, nitro or cyano, R¹⁶ and R¹⁷ independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanoethyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxycarbonylethyl, acetoxyethyl or phenyl and R¹⁶ additionally represents hydrogen or NR¹⁶R¹⁷ represents pyrrolidino, piperidino or morpholino, and An⁻ represents tetrafluoroborate, perchlorate, hexafluorosilicate, hexafluorophosphate, iodide, rhodanide, cyanate, hydroxy acetate, methoxy acetate, lactate, citrate, methane sulphonate, ethane sulphonate, benzene sulphonate, toluene sulphonate, butylbenzene sulphonate, chlorobenzene sulphonate, dodecylbenzene sulphonate or naphthalene sulphonate, wherein all alkyl radicals can be branched.
 6. An optical data storage medium according to one or more of claims 1 to 4, characterized in that the diaza hemicyanine corresponds to the (X) to (XIII)

in which R¹ and R² independantly of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanomethyl, cyanoethyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl or a radical of the formula

X¹ represents O and X³ represents CH or X¹ represents S and X³ represents N, CH or C—CN, R³ and R⁴ independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanoethyl, N hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxycarbonylethyl or acetoxyethyl or NR³R⁴ represents pyrrolidino, piperidino or morpholino, R⁹ represents hydrogen, R¹³, R¹⁴ and R¹⁵ independently of one another represent hydrogen, methyl, methoxy, cloro, nitro or cyano, R¹⁶ and R¹⁷ independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanoethyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxycarbonylethyl, acetoxyethyl or phenyl and R¹⁶ additionally represents hydrogen or NR¹⁶R¹⁷ represents pyrrolidino, piperidino or morpholino, and An⁻ represents tetrafluoroborate, perchlorate, hexafluorosilicate, hexafluorophosphate, iodide, rhodanide, cyanate, hydroxy acetate, methoxy acetate, lactate, citrate, methane sulphonate, ethane sulphonate, benzene sulphonate, toluene sulphonate, butylbenzene sulphonate, chlorobenzene sulphonate, dodecylbenzene sulphonate or naphthalene sulphonate, wherein all alkyl radicals can be branched.
 7. An optical data storage medium according to one or more of claims 1 to 4, characterized in that the diaza hemicyanine corresponds to the formula (XIV) to (XVII)

in which R¹, R² and R¹² independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanomethyl, cyanoethyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl or a radical of the formula

R¹³, R¹⁴ and R¹⁵ independently of one another represent hydrogen, methyl, methoxy, chloro, nitro or cyano, R¹⁶ and R¹⁷ independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanoethyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxycarbonylethyl, acetoxyethyl or phenyl and R¹⁶ additionally represents hydrogen or NR¹⁶R¹⁷ represents pyrrolidino, piperidino or morpholino, R¹¹ represents hydrogen, methyl or phenyl and An⁻represents tetrafluoroborate, perchlorate, hexafluorosilicate, hexafluorophosphate, iodide, rhodanide, cyanate, hydroxy acetate, methoxy acetate, lactate, citrate, methane sulphonate, ethane sulphonate, benzene sulphonate, toluene sulphonate, butylbenzene sulphonate, chlorobenzene sulphonate, dodecylbenzene sulphonate or naphthalene sulphonate, wherein all alkyl radicals can be branched.
 8. Diaza hemicyanines corresponding to the formula (I)

in which R¹, A, X², K amd An⁻ have he meaning of claim
 2. 9. The use of diaza hemicyanines in the information layer of recordable optical data storage media, wherein the hemicyanines have an absorption maximum λ_(max2) in the range from 420 to 650 nm.
 10. The use of diaza hemicyanines in the information layer of recordable optical data storage media, wherein the data storage media are recorded on and read with a blue laser light.
 11. A process for producing the optical data storage media according to claim 1, which is characterized in that a preferably transparent substrate, which has optionally already been coated with a reflecting layer, is coated with the hemicyanines, optionally in combination with suitable binders and additives and optionally suitable solvents, and is optionally provided with a reflecting layer, additional intermediate layers and optionally a protective layer or an additional substrate or a top layer.
 12. Optical data storage media according to claim 1 which have been recorded on using blue or red, in particular blue light, and especially blue laser light. 